Waiting for response or lower my expectation

Recently, I was given a verbal offer and HR said they would send me the formal one by the end of the week. But when I followed up, HR told me that because the internal approval process changed, they need to do everything all over again. And he is not sure if I would still get an offer or not and it might take weeks for them to give a response. I was shocked. I don't know if I should still keep hopeful. I probably will follow up after several weeks but this thing just make me feel very frustrated. Please share your thinking. Thank you so much!